I'm guessing that your money problems are coming from the fact that you have a lot of men garrisoned, and you're not winning any spoils of war while attempting to seige the nords. If you are worried about losing every Denar you own, I'd consider giving up the seige dream for now and replenish your treasury (and your morale).
When it comes to the seiging of the Nords, as everyone here has said before me, arrows are the Nords weak point. The problem here is that most archer units only hold around 30 arrows, while infantry can swing an axe an infinate amount of times. You have to learn how to make those arrows count (and yes, this is where your HOLD FIRE command would come in very handy). Each castle is different when it comes to where the best place to put your archers, but you get the hang of it after a few times, and it becomes fairly intuitive where they will most likely do well after you try it a few times.
The problem is deciding what type of archer you need. If you are going to stay way back and fire from afar, the Rhoddock Sharpshooter works best in my opinion. But if you find that it works better to shoot from near the ladder I like the Khergit Veteran Horse Archers. They use short bows which fire faster, and the Khergit use Khergit Arrows which hold 4 more arrows than your average bundle.
On the bright side, a lot of Huscarls use 2 handed weapons which leave them vulnerable to ranged weapons. The down side is that no matter how many you take with arrows on the ground, there will always be more infantry at the top of the ladder at the front line than you can use until you beat them off of the top. You have to find a way to level the playing field once your archers run out of arrows (or if you like, you can send the first wave of archers to their deaths to make way for the second wave of fresh archers). I hope you have a strong shield with you and you know how to use it, because there is only one person who can hold the line at the top to let the others get up there to fight the fair fight, and that's you.